Combustion device and boiler

ABSTRACT

A combustion device includes: a burner including an ammonia injection nozzle having a tip portion provided with an injection port facing an internal space of a furnace; an adjustment structure that adjusts a temperature of the tip portion; and
         a control device that controls an operation of the adjustment structure so that the temperature of the tip portion is equal to or lower than a reference temperature.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of International Application No. PCT/JP2021/039361, filed on Oct. 25, 2021, which claims priority to Japanese Patent Application No. 2021-025118, filed on Feb. 19, 2021, the entire contents of which are incorporated by reference herein.

BACKGROUND ART Technical Field

The present disclosure relates to a combustion device and a boiler. This application claims the benefit of priority based on Japanese Patent Application No. 2021-025118 filed on Feb. 19, 2021, the contents of which are incorporated herein by reference.

Related Art

Among burners provided in a furnace such as a boiler, there is a burner having an ammonia injection nozzle that injects ammonia as fuel. By using ammonia as fuel, carbon dioxide emissions are reduced. For example, Patent Literature 1 discloses a burner that mixes and combusts pulverized coal and ammonia as fuel.

CITATION LIST Patent Literature

-   -   Patent Literature 1: JP 2019-086189 A

SUMMARY Technical Problem

By the way, in the burner having the ammonia injection nozzle, ammonia is injected from an injection port provided at a tip portion of the ammonia injection nozzle, and thus flame is formed in front of the burner. The tip portion of the ammonia injection nozzle is exposed to an atmosphere containing ammonia and having a high temperature, and thus is easily nitrided. Therefore, it is desirable to suppress nitriding of the ammonia injection nozzle in order to suppress reduction in toughness due to nitriding of the tip portion of the ammonia injection nozzle.

An object of the present disclosure is to provide a combustion device and a boiler capable of suppressing nitriding of the ammonia injection nozzle.

Solution to Problem

In order to solve the above problems, a combustion device of the present disclosure includes: a burner including an ammonia injection nozzle having a tip portion provided with an injection port facing an internal space of a furnace; an adjustment structure that adjusts a temperature of the tip portion; and a control device that controls an operation of the adjustment structure so that the temperature of the tip portion is equal to or lower than a reference temperature.

The adjustment structure may include a mechanism that adjusts a flow rate of ammonia in the ammonia injection nozzle.

The adjustment structure may include a mechanism that adjusts a separation distance between the injection port and the internal space.

The adjustment structure may include a mechanism that adjusts an opening area of the injection port.

The combustion device may include an air pipe disposed coaxially with the ammonia injection nozzle so as to surround the ammonia injection nozzle, and the adjustment structure may include a mechanism that adjusts a flow rate of air in the air pipe.

In order to solve the above problems, a boiler according to the present disclosure includes the combustion device described above.

Effects of Disclosure

According to the present disclosure, it is possible to suppress nitriding of the ammonia injection nozzle.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a boiler according to the present embodiment.

FIG. 2 is a schematic diagram illustrating a combustion device according to the present embodiment.

FIG. 3 is a flowchart illustrating an example of a flow of processing performed by a control device according to the present embodiment.

FIG. 4 is a schematic diagram illustrating a combustion device according to a first modification.

FIG. 5 is a schematic diagram illustrating a state in which a tip portion temperature is higher in the combustion device according to the first modification than in an example of FIG. 4 .

FIG. 6 is a schematic diagram illustrating the combustion device according to a second modification.

FIG. 7 is a schematic diagram illustrating a state in which the tip portion temperature is higher in the combustion device according to the second modification than in an example of FIG. 6 .

FIG. 8 is a schematic diagram illustrating the combustion device according to a third modification.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Dimensions, materials, other specific numerical values, and the like shown in the embodiments are merely examples for facilitating understanding, and do not limit the present disclosure unless otherwise specified. Note that in the present specification and the drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, redundant description is omitted, and elements not directly related to the present disclosure are not illustrated.

FIG. 1 is a schematic diagram illustrating a boiler 1 according to the present embodiment. As illustrated in FIG. 1 , a boiler 1 includes a furnace 2, a flue gas duct 3, and a burner 4.

The furnace 2 is a furnace that burns fuel to generate combustion heat. Hereinafter, an example in which ammonia and pulverized coal are used as fuel in the furnace 2 will be mainly described. By using ammonia and pulverized coal as fuel, carbon dioxide emissions are reduced. However, as described later, the fuel used in the furnace 2 is not limited to this example.

The furnace 2 has a cylindrical shape (for example, a rectangular cylindrical shape) extending in a vertical direction. In the furnace 2, high-temperature combustion gas is generated by combustion of the fuel. A bottom portion of the furnace 2 is provided with a discharge port 2 a for discharging ash content generated by the combustion of the fuel to the outside.

The flue gas duct 3 is a path for guiding the combustion gas generated in the furnace 2 to the outside as exhaust gas. The flue gas duct 3 is connected with an upper portion of the furnace 2. The flue gas duct 3 has a horizontal flue gas duct 3 a and a rear flue gas duct 3 b. The horizontal flue gas duct 3 a extends horizontally from the upper portion of the furnace 2. The rear flue gas duct 3 b extends downwardly from an end portion of the horizontal flue gas duct 3 a.

The boiler 1 includes a superheater (not illustrated) provided in the upper portion or the like of the furnace 2. In the superheater, heat is exchanged between combustion heat generated in the furnace 2 and water. Accordingly, water vapor is generated. Further, the boiler 1 may include various devices (for example, a repeater, an economizer, an air preheater, or the like) not illustrated in FIG. 1 .

The burner 4 is provided in a lower wall portion of the furnace 2. The furnace 2 is provided with a plurality of burners 4 at intervals in a circumferential direction of the furnace 2. Note that although not illustrated in FIG. 1 , the plurality of burners 4 are also provided at intervals in an extending direction (an up-down direction) of the furnace 2. The burner 4 injects ammonia and pulverized coal as fuel into the furnace 2. The fuel injected from the burner 4 burns to form a flame F in the furnace 2. Note that the furnace 2 is provided with an ignition device (not illustrated) that ignites the fuel injected from the burner 4.

FIG. 2 is a schematic diagram illustrating a combustion device 100 according to the present embodiment. As illustrated in FIG. 2 , the combustion device 100 includes a burner 4, an air supply unit 5, an ammonia tank 6, an adjustment structure 7 (specifically, a mechanism including a flow rate control valve 71), a temperature sensor 8, and a control device 9.

The burner 4 is attached to a wall portion of the furnace 2 outside the furnace 2. The burner 4 includes an ammonia injection nozzle 41, an air injection nozzle 42, and a pulverized coal injection nozzle 43. The ammonia injection nozzle 41 is a nozzle that injects ammonia. The air injection nozzle 42 is a nozzle that injects combustion air.

The pulverized coal injection nozzle 43 is a nozzle that injects the pulverized coal.

The ammonia injection nozzle 41, the air injection nozzle 42, and the pulverized coal injection nozzle 43 each have a cylindrical shape. The air injection nozzle 42 is disposed coaxially with the ammonia injection nozzle 41 so as to surround the ammonia injection nozzle 41. The pulverized coal injection nozzle 43 is disposed coaxially with the air injection nozzle 42 so as to surround the air injection nozzle 42. The ammonia injection nozzle 41, the air injection nozzle 42, and the pulverized coal injection nozzle 43 form a triple cylindrical structure. Central axes of the ammonia injection nozzle 41, the air injection nozzle 42, and the pulverized coal injection nozzle 43 intersect (specifically, are substantially perpendicular to) the wall portion of the furnace 2.

Hereinafter, a radial direction of the burner 4, an axial direction of the burner 4, and a circumferential direction of the burner 4 are also simply referred to as a radial direction, an axial direction, and a circumferential direction. A furnace 2 side (right side of FIG. 2 ) of the burner 4 is referred to as a tip side, and a side (left side of FIG. 2 ) opposite to the furnace 2 side of the burner 4 is referred to as a rear end side.

The ammonia injection nozzle 41 includes a main body 41 a, a supply port 41 b, and an injection port 41 c. The main body 41 a has a cylindrical shape. The main body 41 a extends on a central axis of the burner 4. A wall thickness, an inner diameter, and an outer diameter of the main body 41 a are substantially constant regardless of an axial position. However, the wall thickness, the inner diameter, and the outer diameter of the main body 41 a may change depending on the axial position. The supply port 41 b that is an opening is provided at a rear end portion of the main body 41 a. The supply port 41 b is connected to the ammonia tank 6. The injection port 41 c that is an opening is provided at a tip portion of the main body 41 a. The injection port 41 c faces an internal space of the furnace 2. That is, the injection port 41 c is directed to the internal space of the furnace 2.

The ammonia is supplied from the ammonia tank 6 into the main body 41 a through the supply port 41 b. As indicated by arrow A1, the ammonia supplied into the main body 41 a flows in the main body 41 a. The ammonia that has passed through the main body 41 a is injected from the injection port 41 c toward the internal space of the furnace 2. In this manner, the ammonia injection nozzle 41 is provided toward the internal space of the furnace 2.

The air injection nozzle 42 includes a main body 42 a and an injection port 42 b. The main body 42 a has a cylindrical shape. The main body 42 a is disposed coaxially with the main body 41 a of the ammonia injection nozzle 41 so as to surround the main body 41 a. The main body 42 a has a tapered shape toward the tip side. A supply port (not illustrated) is provided in a rear portion (that is, a portion on the rear end side) of the main body 42 a.

The supply port of the air injection nozzle 42 is connected to an air supply source (not illustrated). For example, the supply port of the air injection nozzle 42 is exposed to the atmosphere as the air supply source. The injection port 42 b that is an opening is provided at a tip portion of the main body 42 a. The tip portion of the main body 41 a of the ammonia injection nozzle 41 is located radially inside the tip portion of the main body 42 a. The injection port 42 b is an annular opening between the tip portion of the main body 42 a and the tip portion of the main body 41 a of the ammonia injection nozzle 41. The injection port 42 b faces the internal space of the furnace 2. That is, the injection port 42 b is directed to the internal space of the furnace 2.

Air is supplied from the air supply source (for example, the atmosphere) into the main body 42 a via the supply port (not illustrated). As illustrated by arrow A2, the air supplied into the main body 42 a flows in a space between an inner peripheral portion of the main body 42 a and an outer peripheral portion of the main body 41 a of the ammonia injection nozzle 41. The air that has passed through the main body 42 a is injected from the injection port 42 b toward the internal space of the furnace 2. In this manner, the air injection nozzle 42 is provided toward the internal space of the furnace 2.

The pulverized coal injection nozzle 43 includes a main body 43 a and an injection port 43 b. The main body 43 a has a cylindrical shape. The main body 43 a is disposed coaxially with the main body 42 a of the air injection nozzle 42 so as to surround the main body 42 a. The main body 43 a has a tapered shape toward the tip side. A supply port (not illustrated) is provided in a rear portion (that is, a portion on the rear end side) of the main body 43 a.

The supply port of the pulverized coal injection nozzle 43 is connected to a pulverized coal supply source (not illustrated). The injection port 43 b that is an opening is provided at a tip portion of the main body 43 a. An axial position of a tip of the main body 43 a substantially coincides with an axial position of a tip of the main body 42 a of the air injection nozzle 42. The injection port 43 b is an annular opening between the tip portion of the main body 43 a and the tip portion of the main body 42 a of the air injection nozzle 42. The injection port 43 b faces the internal space of the furnace 2. That is, the injection port 43 b is directed to the internal space of the furnace 2.

The pulverized coal is supplied into the main body 43 a from the pulverized coal supply source via a supply port (not illustrated) together with air for conveying the pulverized coal. As illustrated by arrow A3, the pulverized coal supplied into the main body 43 a flows together with the air in a space between the inner peripheral portion of the main body 43 a and the outer peripheral portion of the main body 42 a of the air injection nozzle 42. The pulverized coal that has passed through the main body 43 a is injected from the injection port 43 b toward the internal space of the furnace 2. In this manner, the pulverized coal injection nozzle 43 is provided toward the internal space of the furnace 2.

The air supply unit 5 supplies the combustion air to a flame (see a flame F in FIG. 1 ) formed by the burner 4 from radially outside. The air supply unit 5 is disposed to cover between the tip portion of the burner 4 and the furnace 2. A flow path 51 through which the air flows is formed in the air supply unit 5. The flow path 51 is formed in a cylindrical shape coaxial with the burner 4. The flow path 51 is connected to the air supply source (not illustrated). An injection port 52 is formed at an end portion of the flow path 51 on the furnace 2 side.

As illustrated by arrow A4, the air supplied from the air supply source to the air supply unit 5 passes through the flow path 51 and is injected from the injection port 52 toward the internal space of the furnace 2. The injection port 52 faces the internal space of the furnace 2. That is, the injection port 52 is directed to the internal space of the furnace 2. In this manner, the air supply unit 5 is provided toward the internal space of the furnace 2. The air injected from the injection port 52 of the air supply unit 5 advances toward the internal space of the furnace 2 while swirling in the circumferential direction.

The adjustment structure 7 is a mechanism for adjusting a temperature (hereinafter, also referred to as a tip portion temperature) of a tip portion of the ammonia injection nozzle 41. The tip portion of the ammonia injection nozzle 41 is a portion of the ammonia injection nozzle 41 near the injection port 41 c (for example, a portion within a predetermined distance rearwardly from the injection port 41 c in the axial direction).

In the present embodiment, the adjustment structure 7 adjusts the tip portion temperature of the ammonia injection nozzle 41 by adjusting a flow rate of ammonia (hereinafter, also referred to as an ammonia flow rate) in the ammonia injection nozzle 41. The adjustment structure 7 includes a flow rate control valve 71.

The flow rate control valve 71 controls the flow rate of ammonia supplied from the ammonia tank 6 to the ammonia injection nozzle 41. The flow rate control valve 71 is provided in a flow path connecting the ammonia tank 6 and the supply port 41 b of the ammonia injection nozzle 41. By adjusting an opening degree of the flow rate control valve 71, the flow rate of ammonia supplied from the ammonia tank 6 to the ammonia injection nozzle 41 is adjusted. Accordingly, the flow rate of ammonia (that is, the ammonia flow rate) in the ammonia injection nozzle 41 is adjusted. Specifically, the ammonia flow rate increases as the opening degree of the flow rate control valve 71 increases.

Note that in the ammonia tank 6, the ammonia is stored in a liquid state. The ammonia stored in the ammonia tank 6 is vaporized by a vaporizer. Vaporized ammonia is supplied to the ammonia injection nozzle 41 through the flow rate control valve 71.

Here, the tip portion of the ammonia injection nozzle 41 is cooled by ammonia flowing through the ammonia injection nozzle 41. As the ammonia flow rate increases, cooling capacity by the ammonia flowing through the ammonia injection nozzle 41 (that is, ability to cool the tip portion of the ammonia injection nozzle 41) increases. Therefore, the adjustment structure 7 can adjust the tip portion temperature of the ammonia injection nozzle 41 by adjusting the ammonia flow rate.

The temperature sensor 8 detects the tip portion temperature of the ammonia injection nozzle 41. The temperature sensor 8 is provided at the tip portion of the ammonia injection nozzle 41, and detects a temperature at an installation position of the temperature sensor 8. Note that the temperature sensor 8 may be provided on an outer peripheral side or an inner peripheral side of the tip portion of the ammonia injection nozzle 41. As the temperature sensor 8, various types of sensors that can be used in a high-temperature environment can be used. A detection result by the temperature sensor 8 is output to the control device 9.

The control device 9 includes a central processing unit (CPU), a ROM for storing a program and the like, a RAM as a work area, and the like, and controls the entire combustion device 100. In particular, the control device 9 controls an operation of the adjustment structure 7. Specifically, the control device 9 can adjust the ammonia flow rate and adjust the tip portion temperature of the ammonia injection nozzle 41 by controlling the opening degree of the flow rate control valve 71 of the adjustment structure 7.

FIG. 3 is a flowchart illustrating an example of a flow of processing performed by the control device 9 according to the present embodiment. A processing flow illustrated in FIG. 3 is executed, for example, at all times (that is, repeatedly) in order to accurately control the tip portion temperature of the ammonia injection nozzle 41.

When the processing flow illustrated in FIG. 3 starts, in step S101, the control device 9 obtains the tip portion temperature of the ammonia injection nozzle 41. For example, the control device 9 obtains the tip portion temperature of the ammonia injection nozzle 41 from the temperature sensor 8.

By obtaining the detection result of the temperature sensor 8 as the tip portion temperature of the ammonia injection nozzle 41, the tip portion temperature of the ammonia injection nozzle 41 can be accurately obtained. However, the control device 9 may obtain information (for example, a temperature of atmosphere around the tip portion of the ammonia injection nozzle 41) other than the detection result of the temperature sensor 8 as information for estimating the tip portion temperature of the ammonia injection nozzle 41.

After step S101, in step S102, the control device 9 sets a target opening degree of the flow rate control valve 71 so that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than a reference temperature. As will be described later, the opening degree of the flow rate control valve 71 is controlled to the target opening degree.

Here, the tip portion of the ammonia injection nozzle 41 is exposed to an atmosphere containing ammonia and having a high temperature, and thus is easily nitrided. The tip portion of the ammonia injection nozzle 41 is heated by radiant heat from the internal space of the furnace 2 in which the flame F is formed. Nitriding of the tip portion of the ammonia injection nozzle 41 is more likely to occur as the tip portion temperature is raised. The reference temperature is a temperature equal to or lower than a lower limit value of a nitriding temperature range that is a temperature range in which the nitriding of the tip portion of the ammonia injection nozzle 41 is likely to occur. That is, when the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature, the nitriding of the tip portion of the ammonia injection nozzle 41 is suppressed.

In step S102, the control device 9 sets the target opening degree of the flow rate control valve 71 on the basis of the tip portion temperature of the ammonia injection nozzle 41. The control device 9 sets a larger opening degree as the target opening degree as the tip portion temperature of the ammonia injection nozzle 41 is higher. Accordingly, the higher the tip portion temperature of the ammonia injection nozzle 41, the higher the ammonia flow rate, and the higher the cooling capacity by the ammonia flowing through the ammonia injection nozzle 41. Therefore, it is appropriately achieved that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature.

After step S102, in step S103, the control device 9 controls the flow rate control valve 71 so that the opening degree of the flow rate control valve 71 is the target opening degree, and the processing flow illustrated in FIG. 3 ends.

As described above, in the combustion device 100 according to the present embodiment, the adjustment structure 7 adjusts the ammonia flow rate. Accordingly, adjustment of the tip portion temperature of the ammonia injection nozzle 41 is appropriately achieved. The control device 9 controls the operation of the adjustment structure 7 so that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature.

Accordingly, it is possible to suppress that the tip portion temperature of the ammonia injection nozzle 41 is raised to the nitriding temperature range in which nitriding is likely to occur. Therefore, the nitriding of the ammonia injection nozzle 41 is suppressed. Consequently, reduction in toughness due to the nitriding of the ammonia injection nozzle 41 is suppressed. Accordingly, for example, it is possible to suppress a decrease in stability of combustion due to thinning of the tip portion of the ammonia injection nozzle 41. In addition, for example, a frequency of repairing the ammonia injection nozzle 41 can be reduced.

In particular, the control device 9 controls the operation of the adjustment structure 7 such that the ammonia flow rate is increased (that is, the tip portion of the ammonia injection nozzle 41 is more easily cooled) as the tip portion temperature of the ammonia injection nozzle 41 is higher. Accordingly, it is appropriately achieved that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature.

Note that since a main purpose of ammonia injected from the ammonia injection nozzle 41 is to be used as the fuel of the burner 4, the ammonia flow rate is controlled with absolute priority given to ensuring the flow rate required as the fuel. For example, when the ammonia flow rate required for securing the cooling capacity by the ammonia flowing through the ammonia injection nozzle 41 (that is, the ammonia flow rate required to make the tip portion temperature of the ammonia injection nozzle 41 equal to or lower than the reference temperature) is lower than a flow rate required as the fuel, the control device 9 controls the operation of the adjustment structure 7 so that the ammonia flow rate is the flow rate required as the fuel.

In the above description, an example has been described in which the adjustment structure 7 adjusts the tip portion temperature of the ammonia injection nozzle 41 by adjusting the ammonia flow rate. However, the adjustment structure 7 is not limited to the above example as long as it has a function of adjusting the tip portion temperature of the ammonia injection nozzle 41. Hereinafter, modifications in which adjustment structures 7A, 7B, and 7C different from the adjustment structure 7 of the combustion device 100 are used will be described.

FIG. 4 is a schematic diagram illustrating a combustion device 100A according to a first modification. As illustrated in FIG. 4 , the combustion device 100 A is an example in which the adjustment structure 7 is replaced with an adjustment structure 7A in the combustion device 100 described above.

The adjustment structure 7A adjusts a separation distance between the injection port 41 c of the ammonia injection nozzle 41 and the internal space of the furnace 2 to adjust the tip portion temperature of the ammonia injection nozzle 41. The adjustment structure 7A includes a drive device 71A.

The drive device 71A moves the main body 41 a of the ammonia injection nozzle 41 in the axial direction. For example, the drive device 71A includes a mechanism that guides movement of the main body 41 a of the ammonia injection nozzle 41 in the axial direction, and a device (for example, a motor or the like) that generates power. Then, the drive device 71A can move the main body 41 a in the axial direction by transmitting the power to a rear portion of the main body 41 a of the ammonia injection nozzle 41.

The adjustment structure 7A can adjust the separation distance between the injection port 41 c of the ammonia injection nozzle 41 and the internal space of the furnace 2 by moving the main body 41 a of the ammonia injection nozzle 41 in the axial direction by the drive device 71A.

As described above, the tip portion of the ammonia injection nozzle 41 is heated by the radiant heat from the internal space of the furnace 2 in which the flame F is formed. As the separation distance between the injection port 41 c of the ammonia injection nozzle 41 and the internal space of the furnace 2 is longer (that is, as the injection port 41 c is farther from the internal space of the furnace 2), the tip portion of the ammonia injection nozzle 41 is less likely to be heated by the radiant heat from the internal space of the furnace 2. Therefore, the adjustment structure 7A can adjust the tip portion temperature of the ammonia injection nozzle 41 by adjusting the separation distance between the injection port 41 c of the ammonia injection nozzle 41 and the internal space of the furnace 2.

Similarly to the combustion device 100 described above, the control device 9 controls an operation of the adjustment structure 7A so that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature. Specifically, the control device 9 controls an operation of the drive device 71A such that the main body 41 a of the ammonia injection nozzle 41 moves outwardly of the furnace 2 as the tip portion temperature of the ammonia injection nozzle 41 is higher. Accordingly, the control device 9 can control the operation of the adjustment structure 7A such that the injection port 41 c of the ammonia injection nozzle 41 moves outwardly of the furnace 2 as the tip portion temperature of the ammonia injection nozzle 41 is higher. In other words, the control device 9 can control the operation of the adjustment structure 7A such that the separation distance between the injection port 41 c and the internal space of the furnace 2 is increased as the tip portion temperature of the ammonia injection nozzle 41 is higher. Therefore, since the extent to which the tip portion of the ammonia injection nozzle 41 is heated by the radiant heat from the furnace 2 is reduced, it is appropriately achieved that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature.

FIG. 5 is a schematic diagram illustrating a state in which the tip portion temperature is higher in the combustion device 100A according to the first modification than in an example of FIG. 4 . In an example of FIG. 5 , the tip portion temperature is higher than that in the example of FIG. 4 . Consequently, the main body 41 a of the ammonia injection nozzle 41 has moved outwardly of the furnace 2 as compared with the example of FIG. 4 . Accordingly, the injection port 41 c of the ammonia injection nozzle 41 has moved outwardly of the furnace 2 as compared with the example of FIG. 4 . Specifically, the axial position of the injection port 41 c is closer to the furnace 2 than the axial positions of the injection port 42 b and the injection port 43 b in the example of FIG. 4 , but substantially coincides with the axial positions of the injection port 42 b and the injection port 43 b in the example of FIG. 5 . Therefore, the extent to which the tip portion of the ammonia injection nozzle 41 is heated by the radiant heat from the furnace 2 is reduced.

As described above, in the combustion device 100A according to the first modification, the adjustment structure 7A adjusts the separation distance between the injection port 41 c of the ammonia injection nozzle 41 and the internal space of the furnace 2. Accordingly, adjustment of the tip portion temperature of the ammonia injection nozzle 41 is appropriately achieved. The control device 9 controls the operation of the adjustment structure 7A so that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature. Accordingly, the nitriding of the ammonia injection nozzle 41 is suppressed similarly to the combustion device 100 described above.

In particular, the control device 9 controls the operation of the adjustment structure 7A such that the injection port 41 c of the ammonia injection nozzle 41 moves outwardly of the furnace 2 (that is, the tip portion of the ammonia injection nozzle 41 is less likely to be heated) as the tip portion temperature of the ammonia injection nozzle 41 is higher. Accordingly, it is appropriately achieved that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature.

In the above description, an example has been described in which the drive device 71A is provided as the adjustment structure 7A that adjusts the separation distance between the injection port 41 c of the ammonia injection nozzle 41 and the internal space of the furnace 2, and the main body 41 a of the ammonia injection nozzle 41 is moved in the axial direction by the drive device 71A. However, the adjustment structure 7A is not limited to the above example as long as it has a function of adjusting the separation distance between the injection port 41 c of the ammonia injection nozzle 41 and the internal space of the furnace 2. For example, the main body 41 a of the ammonia injection nozzle 41 can expand and contract in the axial direction, and the adjustment structure 7A may adjust the separation distance between the injection port 41 c and the internal space of the furnace 2 by expanding and contracting the main body 41 a in the axial direction by the drive device 71A.

FIG. 6 is a schematic diagram illustrating a combustion device 100B according to a second modification. As illustrated in FIG. 6 , the combustion device 100B is an example in which the adjustment structure 7 is replaced with an adjustment structure 7B in the combustion device 100 described above.

The adjustment structure 7B adjusts an opening area of the injection port 41 c of the ammonia injection nozzle 41 to adjust the tip portion temperature of the ammonia injection nozzle 41. The adjustment structure 7B includes a drive device 71B.

In the combustion device 100B according to the second modification, a variable portion 41 d is provided at the tip portion of the ammonia injection nozzle 41. The variable portion 41 d can adjust the opening area of the injection port 41 c by being deformed. For example, the variable portion 41 d includes a plurality of members spaced apart in the circumferential direction, and can be deformed to have an inclined orientation in which a tip of each member is located radially inward of a rear end thereof. As such a variable portion 41 d, for example, a structure similar to that of a convergent-divergent nozzle can be employed.

The drive device 71B deforms the variable portion 41 d of the ammonia injection nozzle 41. For example, the drive device 71B includes a device (for example, a motor or the like) that is provided at a rear end of the variable portion 41 d and generates power. Then, the driving device 71B can change an orientation of the variable portion 41 d by rotating the variable portion 41 d about the rear end of the variable portion 41 d.

The adjustment structure 7B can adjust the opening area of the injection port 41 c of the ammonia injection nozzle 41 by deforming the variable portion 41 d of the ammonia injection nozzle 41 by the drive device 71B.

As described above, the tip portion of the ammonia injection nozzle 41 is cooled by the ammonia flowing through the ammonia injection nozzle 41. As the opening area of the injection port 41 c of the ammonia injection nozzle 41 is smaller, an injection speed of the ammonia injected from the ammonia injection nozzle 41 is higher. Therefore, the cooling capacity by the ammonia flowing near the tip portion of the ammonia injection nozzle 41 (that is, the ability to cool the tip portion of the ammonia injection nozzle 41) increases. Consequently, the adjustment structure 7B can adjust the tip portion temperature of the ammonia injection nozzle 41 by adjusting the opening area of the injection port 41 c of the ammonia injection nozzle 41.

Similarly to the combustion device 100 described above, the control device 9 controls the operation of the adjustment structure 7B so that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature. Specifically, the control device 9 controls an operation of the drive device 71B such that a radial position of a tip of the variable portion 41 d moves radially inwardly as the tip portion temperature of the ammonia injection nozzle 41 is higher. Accordingly, the control device 9 can control the operation of the adjustment structure 7B such that the opening area of the injection port 41 c of the ammonia injection nozzle 41 is reduced as the tip portion temperature of the ammonia injection nozzle 41 is higher. Therefore, since the injection speed of the ammonia injected from the ammonia injection nozzle 41 is increased and the cooling capacity by the ammonia flowing near the tip portion of the ammonia injection nozzle 41 is increased, it is appropriately achieved that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature.

FIG. 7 is a schematic diagram illustrating a state in which the tip portion temperature is higher in the combustion device 100B according to the second modification than in an example of FIG. 6 . In the example of FIG. 6 , the variable portion 41 d of the ammonia injection nozzle 41 has a cylindrical shape extending in the axial direction of the burner 4. In an example of FIG. 7 , the tip portion temperature is higher than that in the example of FIG. 6 . Therefore, the variable portion 41 d is deformed such that the radial position of the tip of the variable portion 41 d moves radially inwardly. Accordingly, the shape of the variable portion 41 d is a tapered shape toward the tip side (a truncated cone shape in the example of FIG. 7 ). Therefore, the opening area of the injection port 41 c of the ammonia injection nozzle 41 is reduced, and the injection speed of ammonia is increased.

As described above, in the combustion device 100B according to the second modification, the adjustment structure 7B adjusts the opening area of the injection port 41 c of the ammonia injection nozzle 41. Accordingly, adjustment of the tip portion temperature of the ammonia injection nozzle 41 is appropriately achieved. The control device 9 controls the operation of the adjustment structure 7B so that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature. Accordingly, the nitriding of the ammonia injection nozzle 41 is suppressed similarly to the combustion device 100 described above.

In particular, the control device 9 controls the operation of the adjustment structure 7B such that the opening area of the injection port 41 c of the ammonia injection nozzle 41 is reduced (that is, the tip portion of the ammonia injection nozzle 41 is more easily cooled) as the tip portion temperature of the ammonia injection nozzle 41 is higher. Accordingly, it is appropriately achieved that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature.

In the above description, an example has been described in which the drive device 71B is provided as the adjustment structure 7B that adjusts the opening area of the injection port 41 c of the ammonia injection nozzle 41, and the variable portion 41 d of the tip portion of the ammonia injection nozzle 41 is deformed. However, the adjustment structure 7B is not limited to the above example as long as it has a function of adjusting the opening area of the injection port 41 c of the ammonia injection nozzle 41. For example, when a member that can move or extend radially inwardly from the inner peripheral portion of the tip portion of the main body 41 a of the ammonia injection nozzle 41 is provided, a mechanism including the member and a drive device that drives the member can correspond to the adjustment structure 7B. In addition, for example, when a valve body having a tapered shape toward the tip side is provided inside the tip portion of the ammonia injection nozzle 41, a mechanism including the valve body and a drive device that moves the valve body in the axial direction can correspond to the adjustment structure 7B.

FIG. 8 is a schematic diagram illustrating a combustion device 100C according to a third modification. As illustrated in FIG. 8 , the combustion device 100C is an example in which the adjustment structure 7 is replaced with an adjustment structure 7C in the combustion device 100 described above.

The adjustment structure 7C includes an air pipe 71C, an air supply source 72C, and a flow rate control valve 73C. The air pipe 71C is disposed coaxially with the ammonia injection nozzle 41 so as to surround the ammonia injection nozzle 41. The air is supplied into the air pipe 71C (specifically, into a space between the air pipe 71C and the ammonia injection nozzle 41). The adjustment structure 7C adjusts the tip portion temperature of the ammonia injection nozzle 41 by adjusting a flow rate of the air (hereinafter, also referred to as an air flow rate) in the air pipe 71C. The air pipe 71C includes a main body 71Ca, a supply port 71Cb, and an injection port 71Cc. The main body 71Ca has a cylindrical shape. The main body 71Ca is disposed coaxially with the main body 41 a of the ammonia injection nozzle 41 so as to surround the main body 41 a. However, a central axis of the main body 71Ca and a central axis of the main body 41 a of the ammonia injection nozzle 41 may not strictly coincide with each other, and is only required to be within a predetermined range. A wall thickness, an inner diameter, and an outer diameter of the main body 71Ca are substantially constant regardless of the axial position. However, the wall thickness, the inner diameter, and the outer diameter of the main body 71Ca may change depending on the axial position.

An axial position of a tip of the main body 71Ca substantially coincides with the axial position of the tip of the main body 41 a of the ammonia injection nozzle 41. However, the axial position of the tip of the main body 71Ca may be on the front side (that is, the furnace 2 side) or the rear side of the tip of the main body 41 a of the ammonia injection nozzle 41. An axial position of a rear end of the main body 71Ca substantially coincides with an axial position of a rear end of the main body 41 a of the ammonia injection nozzle 41. However, the axial position of the rear end of the main body 71Ca may be on the front side (that is, the furnace 2 side) or the rear side of the rear end of the main body 41 a of the ammonia injection nozzle 41.

The supply port 71Cb is an annular opening formed between the rear end of the main body 71Ca and the rear end of the main body 41 a of the ammonia injection nozzle 41. The supply port 71Cb is connected to the air supply source 72C. The injection port 71Cc is an annular opening formed between the tip of the main body 71Ca and the tip of the main body 41 a of the ammonia injection nozzle 41. The injection port 71Cc faces the internal space of the furnace 2.

The air is supplied from the air supply source 72C into the main body 71Ca through the supply port 71Cb. The air supplied into the main body 71Ca flows in a space between an inner peripheral portion of the main body 71Ca and the outer peripheral portion of the main body 41 a of the ammonia injection nozzle 41. The air that has passed through the main body 71Ca is injected from the injection port 71Cc toward the internal space of the furnace 2. The air injected from the injection port 71Cc is used for combustion in the furnace 2.

The flow rate control valve 73C controls the flow rate of the air supplied from the air supply source 72C to the air pipe 71C. The flow rate control valve 73C is provided in a flow path connecting the air supply source 72C and the supply port 71Cb of the air pipe 71C. By adjusting the opening degree of the flow rate control valve 73C, the flow rate of ammonia supplied from the air supply source 72C to the air pipe 71C is adjusted. Accordingly, a flow rate of the air (that is, an air flow rate) in the air pipe 71C is adjusted. Specifically, the air flow rate increases as the opening degree of the flow rate control valve 73C increases.

Here, the tip portion of the ammonia injection nozzle 41 is cooled by the air flowing through the air pipe 71C. As the air flow rate increases, cooling capacity by the air flowing through the air pipe 71C (that is, ability to cool the tip portion of the ammonia injection nozzle 41) increases. Therefore, the adjustment structure 7C can adjust the tip portion temperature of the ammonia injection nozzle 41 by adjusting the air flow rate.

Similarly to the combustion device 100 described above, the control device 9 controls the operation of the adjustment structure 7C so that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature. Specifically, the control device 9 increases the opening degree of the flow rate control valve 73C as the tip portion temperature of the ammonia injection nozzle 41 is higher. Accordingly, the higher the tip portion temperature of the ammonia injection nozzle 41, the higher the air flow rate, and the higher the cooling capacity by the air flowing through the air pipe 71C. Therefore, it is appropriately achieved that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature.

As described above, in the combustion device 100C according to the third modification, the adjustment structure 7C adjusts the flow rate of the air (that is, the air flow rate) in the air pipe 71C. Accordingly, adjustment of the tip portion temperature of the ammonia injection nozzle 41 is appropriately achieved. The control device 9 controls the operation of the adjustment structure 7C so that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature. Accordingly, the nitriding of the ammonia injection nozzle 41 is suppressed similarly to the combustion device 100 described above.

In particular, the control device 9 controls the operation of the adjustment structure 7C such that the air flow rate is increased (that is, the tip portion of the ammonia injection nozzle 41 is more easily cooled) as the tip portion temperature of the ammonia injection nozzle 41 is higher. Accordingly, it is appropriately achieved that the tip portion temperature of the ammonia injection nozzle 41 is equal to or lower than the reference temperature.

Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is obvious that a person skilled in the art can conceive various changes or modifications within the scope described in the claims, and it is understood that those changes or modifications naturally belong to the technical scope of the present disclosure.

In the above description, examples have been described in which the adjustment structures (that is, any one of the adjustment structures 7, 7A, 7B, and 7C) different from each other are respectively provided in the combustion devices 100, 100A, 100B, and 100C. However, in the combustion device, two or more adjustment structures among the adjustment structures 7, 7A, 7B, and 7C may be used in combination.

In the above description, an example has been described in which in the burner 4, the air injection nozzle 42 is disposed radially outwardly of the ammonia injection nozzle 41, and the pulverized coal injection nozzle 43 is disposed radially outwardly of the air injection nozzle 42, so that a triple cylindrical structure is formed by the ammonia injection nozzle 41, the air injection nozzle 42, and the pulverized coal injection nozzle 43. However, a configuration of the burner 4 is not limited to the above example. For example, a position of the pulverized coal injection nozzle 43 and a position of the ammonia injection nozzle 41 may be replaced. Further, for example, the air injection nozzle 42 may be omitted from the configuration of the burner 4. In this case, for example, the burner 4 may have a double cylindrical structure, a space on a center side of a space divided by the double cylindrical structure may be a flow path of ammonia, and a space radially outwardly adjacent to the flow path of ammonia may be a flow path of the pulverized coal.

In the above description, the example in which ammonia and pulverized coal are used as the fuel in the furnace 2 has been described. However, the fuel used in the furnace 2 only needs to contain at least ammonia, and is not limited to the above example. For example, the fuel used together with ammonia in the furnace 2 may be a fuel other than the pulverized coal (for example, natural gas, biomass, or the like). Further, for example, the fuel used in the furnace 2 may be only ammonia.

In the above description, examples in which the combustion devices 100, 100A, 100B, and 100C are provided in the furnace 2 of the boiler has been described above. However, the furnace in which the combustion devices 100, 100A, 100B, and 100C are used may be any furnace that generates combustion heat by burning fuel. The combustion devices 100, 100A, 100B, and 100C can be used in various furnaces of equipment other than the boiler.

The present disclosure contributes to stabilization of combustion by a combustion device used for a boiler or the like and a reduction in frequency of repairing the combustion device, and thus can contribute to, for example, the goal 7 “Ensure access to affordable, reliable, sustainable and modern energy” and the goal 13 “Take urgent action to combat climate change and its impacts” of the sustainable development goals (SDGs). 

1. A combustion device comprising: a burner including an ammonia injection nozzle having a tip portion provided with an injection port facing an internal space of a furnace; an adjustment structure that adjusts a temperature of the tip portion; and a control device that controls an operation of the adjustment structure so that the temperature of the tip portion is equal to or lower than a reference temperature.
 2. The combustion device according to claim 1, wherein the adjustment structure includes a mechanism that adjusts a flow rate of ammonia in the ammonia injection nozzle.
 3. The combustion device according to claim 1, wherein the adjustment structure includes a mechanism that adjusts a separation distance between the injection port and the internal space.
 4. The combustion device according to claim 2, wherein the adjustment structure includes a mechanism that adjusts a separation distance between the injection port and the internal space.
 5. The combustion device according to claim 1, wherein the adjustment structure includes a mechanism that adjusts an opening area of the injection port.
 6. The combustion device according to claim 2, wherein the adjustment structure includes a mechanism that adjusts an opening area of the injection port.
 7. The combustion device according to claim 3, wherein the adjustment structure includes a mechanism that adjusts an opening area of the injection port.
 8. The combustion device according to claim 4, wherein the adjustment structure includes a mechanism that adjusts an opening area of the injection port.
 9. The combustion device according to claim 1, comprising an air pipe disposed coaxially with the ammonia injection nozzle so as to surround the ammonia injection nozzle, wherein the adjustment structure includes a mechanism that adjusts a flow rate of air in the air pipe.
 10. The combustion device according to claim 2, comprising an air pipe disposed coaxially with the ammonia injection nozzle so as to surround the ammonia injection nozzle, wherein the adjustment structure includes a mechanism that adjusts a flow rate of air in the air pipe.
 11. The combustion device according to claim 3, comprising an air pipe disposed coaxially with the ammonia injection nozzle so as to surround the ammonia injection nozzle, wherein the adjustment structure includes a mechanism that adjusts a flow rate of air in the air pipe.
 12. The combustion device according to claim 4, comprising an air pipe disposed coaxially with the ammonia injection nozzle so as to surround the ammonia injection nozzle, wherein the adjustment structure includes a mechanism that adjusts a flow rate of air in the air pipe.
 13. The combustion device according to claim 5, comprising an air pipe disposed coaxially with the ammonia injection nozzle so as to surround the ammonia injection nozzle, wherein the adjustment structure includes a mechanism that adjusts a flow rate of air in the air pipe.
 14. The combustion device according to claim 6, comprising an air pipe disposed coaxially with the ammonia injection nozzle so as to surround the ammonia injection nozzle, wherein the adjustment structure includes a mechanism that adjusts a flow rate of air in the air pipe.
 15. The combustion device according to claim 7, comprising an air pipe disposed coaxially with the ammonia injection nozzle so as to surround the ammonia injection nozzle, wherein the adjustment structure includes a mechanism that adjusts a flow rate of air in the air pipe.
 16. The combustion device according to claim 8, comprising an air pipe disposed coaxially with the ammonia injection nozzle so as to surround the ammonia injection nozzle, wherein the adjustment structure includes a mechanism that adjusts a flow rate of air in the air pipe.
 17. A boiler comprising the combustion device according to claim
 1. 